Brake



Oct. 17, 1933.

L. K. SNELL BRAKE Filed'July 5, 1929 2 Sheets-Sheet l f L. K. SNELL Oct.17, 1933.

BRAKE 2 sheets-sheet 2l Filed July 5, 1929 UNITED STATES PATENT OFFICEBRAKE Lyle K. Snell, Detroit, Mich., assignor to Eaton ManufacturingCompany, Cleveland, Ohio, a corporation of Ohio Application July`5,1929. Serial No. 376,003

' 5 claims. (ci. iss-7s) 'Ihis invention relates to vehicle brakes, andin the drum for cooperation with its inner surmore particularly tobrakes of the internal eX-. face. 'Ihis friction device may consist of apanding type. flexible band 13 having arms 14 secured at the An objectof this invention is to provide an ends of the band. The arms 14 areprovided improved form of brake in which quiet and with opposed endbearing portions 15, between 60 efficient cooperation between thefriction device which is disposed a rotatable actuating cam and thebrake drum. is attained. 16. The frictionl device is not rigidlyattached Another object of this invention is to proto the backing plate,but is preferably permitted vide an improved form of brake in which theto oat within the drum for a limited distance.

l0 efficiency and length of life of the friction de- The extent of thefloating movement of the 65 vice are increased by employing a novel formfriction device is limited by the anchor memand arrangement of sectionsor portions of brake ber 17 which is rigidly secured to the backinglining. f plate and forms an abutment which is engaged In the drawingsforming a part of thisappliby one or the other end of the frictiondevice, cation, depending upon the direction of rotation of the 70Figure 1 is a sectional elevation showing one drum. v form-f my improvedbrake. The band 13 of the friction device is pro- Fig. 2 is a sectiontaken on line 2 2 of vided with brake lining which is adapted to be Fig.'-1. pressed against the inner surface of the rotat- 20 Fig. 3 is asectional elevation showing anable drum. The actuating cam is carriedupon 75 other form of my improved brake. a rotatable shaft 17', and uponrotation of this Figure 4 is a section taken on line 4 4 of shaft, thecam spreads the bearing portions of Fig. 3. r the arms apart, causingthe brake lining tobe As heretofore constructed, vehicle brakes havepressed into frictional engagement with the surbeen provided with brakelining having the same face of the drum. In carrying out my inven- 80surface characteristic throughout the entire tlbn, this brake lining iscomposed of portions length of its friction surface. The self-enerorsections 18, 19 and 20, each of which porgizing action which takes placewhen the frictions is vof substantially homogeneous character tiondevice is pressed against the drum causes as represented in thedrawings. The section different sections or portions of the brake lin-18 is selected with such a surface characteristic 85 ing to be pressedagainst the brake drum with -that it will engage the drum with a highcoeffidifferent degrees of pressure. The different prescient offriction. The section 20 is selected with sures which are effective atdifferent sections such a surface characteristic that it will engage ofthe lining cause these different sections to the surface of the drumwith a low coefficient of be heated to different temperatures, and alsofriction. The section 19, which is between the 90 cause these sectionsto wear at different rates. sections 18 and 20, is selected with such asur- In brakes, as heretofore constructed, the porface characteristicthat it will engage the surtions of the brake lining which are pressedface of the drum with a coefllcient of friction against the brake drumwith the heaviest preshaving a value between the coeflicients for thesure wear away more Quickly than other porsections 18 and 20. 95 tionsof the lining. In addition, there l is a. As shown in Fig. 1, the drum10 rotates in a tendency for the portions of the brake liningcounter-clockwise direction when the vehicle is which are pressed mostheavily against the brake travelling ahead. Upon applying the brake thedrum to grab and squeak, resulting in inemsection 18 is pressed againstthe brake drum by a cient and noisy operation.- braking forcetransmitted from the actuating 100 In carrying out my invention thesediiculcam through the arm 14. Likewise, the section ties are overcomeand quiet and efficient opera- 20 is pressed against the brake drum bybraking tion are attained by using sections of brake force transmittedthrough the other arm 14. lining having different coeicients offriction, The rotation of the drum, however, produces a and in the formof brake which I have shown self-energizing effect when the section 18is 105 in Figs. 1 and 2, I employ a rotatable brake pressed against itsmoving surface. This selfdrum l'with which is associated a stationaryenergizing effect causes the brake lining to be backing or anchor plate11 secured to some pressed or wedged against the drum with a. propart ofthe vehicle proper such as the axlegressively increasing degree ofpressure. The

housing 12. A friction device is arranged withunit pressure with whichthe section 19 is pressed 110 against the drum is therefore greater thanthe unit pressure with which the section 18 is pressed against the drum,and likewise the unit pressure 'with which the section 20 is pressedagainst the drum is greater than the unit pressure 'effective upon thesection 19. To achieve the most ecient results I have selected thesesections of brake lining so that section 18` which is pressed againstthe brake drum with the lowest average unit pressure also has a surfacecharacteristic giving the highest coefficient of friction. The section20 which is pressed against the drum with the heaviest -pressure hasbeen selected with a surface characteristic to give the lowest coeicientof friction, 4and the section 19 which is pressed against the drum withan intermediate average unit pressure has been selected with a surfacecharacteristic to give an intermedate coeicient of friction. By thisarrangement of sections having different coefficients of friction, thefrictional resistance between the brake drum and the brake lining willbe more nearly uniform throughout the length of the braking surface ofthe friction device, and by approaching a more nearly uniform conditionof frictional engagement between these parts, the different portions ofthe brake lining will wear at a more uniform rate and, furthermore, thismore uniform frictional engagement will tend to cause a more uniformgeneration of heat thereby prolonging the life of the lining andaffording smooth and eilicient operation of the brake.

In Figs. 3 and 4 of the drawings I have shown my invention applied to abrake of the multipleshoe type. In this embodiment of the invention Iemploy a rotatable brake drum 21 having a stationary backing plate 22associated therewith. The friction device housed 'within the drum forengagement with its inner surface cornprises a primary'shoe 23 and asecondary shoe 24. These shoes are hinged together, at one end by meansof hinge pins 25 and an adjustable connecting rod 26. The opposite endsof the shoes are arranged in opposed relation, and are provided withopposed bearing portions 28 having an actuating cam 29 disposedtherebetween. This friction device is not rigidly connected to thebacking plate but is preferably arranged to oat within the brake drum,the amount of movement of the friction device being limited by theanchor pin 30 which serves as an abutment which is engaged by one or theother of the opposed ends of the shoes, depending upon the direction ofrotation of the drum when the brake is applied. The act`uating cam 29 iscarried on one end of an operating shaft 31 and upon rotation of thisshaft wedges the opposed ends of the shoes apart so as to press thebrake linings 32 and .33, carried by the shoes 23 and 24, respectively,against the surface of the brake drum. As. represented in the drawingseach of these lining portions is substantially homogeneous in character.With the drum moving in a clockwise direction, as shown in Fig. 3,rotation of the actuating cam 29 causes the lining of the primary shoeto be pressed against the brake drum. The frictional engagement betweenthe lining of the primary shoe and the drum tends to carry the shoearound with the drum, and produces a self-energizing effect which causesthe brake lining of the secondary shoe to be heavily pressed against themoving drum.

In carrying out my invention the brake lining for the primary shoe isselected with such a surface characteristic that it will engage thesurface of the drum with a high coefficient of friction, while thelining of the secondary shoe is selected with such a surfacecharacteristic `that it will engage the surface of the drum with a lowcoeiiicient of friction. By selecting the sections of brake lining inthis manner, the shoe which is most heavily pressed' against the brakedrum will have brake lining thereon having a low coeiiicient offriction, and the shoe which is more lightly pressed against the drumwill have brake lining thereon with a high coefficient of friction. Byselecting the brake linings in this manner the different sections oflining will wear at a more uniform rate and likewise, the temperaturesgenerated by the frictional engagement between the drum and the sectionsof ulining will be more uniform with the result that there will be lesstendency to squeak and chatter.

While I have shown a brake liningcomposed of three portions or sectionsin Fig. l, and of two sections inFig; 3, obviously any desired number ofsuch portions or sections could be employed and likewise, while I haveshown in Fig. 3 a brake having only two shoes, it should be understoodthat my invention is equally applicable to various forms of multipleshoe brakes.

While I have shown and described my invention in a detailed manner, itshould be understood, however, that I do not limit my invention to theprecise details shown and described, but 105 regard it as including suchmodications and changes as do not involve a departure from 'the spiritof the invention and the scope of the appended claims.

Having described my invention, I claim:

1. In a brake the combination of a drum, a friction device having aplurality of drum engasing surfaces, and means for actuating said devicewhereby said surfaces engage said drum with different pressures, saidsurfaces being 1,15 formed to engage said drum with coefficients offriction varying in inverse relation to said different pressures.

2. In a brake the combination of a drum, a friction device provided witha plurality of sur- 120 face portions adapted to engage said drum. andmeans for actuating said device whereby said surface portions arepressed against said drum with progressively varying pressure values,the characteristics of said surface portions being 125 such that theyengage said drum with coeicients of friction which vary in inverserelation with said varying pressure values.

3. In a brake the combination of a drum, a friction device associatedwith said drumV including primary and secondary shoes arranged forcooperation with the same surface portion of the drum, the coeflicientof friction between the primary shoe and the surface portion of the drumbeing higher than the coefficient of friction between the secondary shoeand the surface portion of the drum.

4. In a brake the combination of a drum, a friction device associatedwith said drum including primary and secondary shoes arranged forcooperation with the same surface portion of the drum, friction liningon each of 'said' shoes for contact with said surface portion, and meansfor actuating said shoes whereby the lining of the primary shoe ispressed against said 14:6 surface portion with a relatively low unitpressure and the lining of the secondary shoe is pressed against saidsurface portion with a relatively high unit pressure, the frictionlining of said shoes being such that the coemcient of fric- 150 tionbetween the friction lining of said primary shoe and said surfaceportion is relatively high and the coefficient of friction between thefriction lining of said secondary shoe and said surface portion isrelatively low.

5. In a brake the combination of a drum, a friction device forcooperation with said drum and including friction lining having aplurality of portions arranged in a series to extend circumferentiallyof said drum, andmeans for causing said lining 'to frictionally engagesaid drum whereby one portion of said series is pressed against the drumwith a relatively low unit pressure and another portion of the series ispressed against the drum with a relatively high unit pressure, each ofthe portions of the circumferentially extending series beingsubstantially homogeneous in character and said portions being so formedthat the portion of said series Which is pressed against the drum With arelatively low unit pressure has a relatively high coeiicient offriction and the portion of said series which is pressed against thedrum with a relatively high unit pressure has a relatively low coelcientof friction.

LYLE'K. SNEIL.

